1. Field of the Invention
The invention relates to a process for recycling exhaust gases from Fischer-Tropsch synthesis, thereby reducing carbon emissions.
2. Description of the Related Art
Typically, to improve the efficiency of the Fischer-Tropsch synthesis and to eliminate adverse effects of high CO concentration in the raw gas, incompletely reacted raw gas is returned to the inlet of the reactor to mix with fresh raw gas. However, the inert gas in the raw gas tends to accumulate in the reactor, which adversely affects the production efficiency.
The syngas from the gasification of biomass or coal often has a low hydrogen-carbon ratio, which cannot meet the requirement of the Fischer-Tropsch synthesis. In general, the raw gas is treated by water-gas shift reaction and decarbonization processes to regulate the hydrogen-carbon ratio for the Fischer-Tropsch synthesis. However, the gasification, the shift reaction, and the decarbonization are complex and require relatively high investment in the apparatus. In addition, the Fischer-Tropsch synthesis necessitates additional hydrogen for processing the product and reducing the catalyst, which increases the production costs.